Onsager vortex formation in Bose-Einstein condensates in two-dimensional power-law traps

TL;DR

This study computationally investigates vortex dynamics in 2D Bose-Einstein condensates within various trap shapes, revealing that steep traps promote Onsager vortex clusters while harmonic traps suppress them, with implications for experimental observation.

Contribution

It demonstrates how trap shape influences Onsager vortex formation and provides insights into vortex interactions and heating mechanisms in Bose-Einstein condensates.

Findings

Onsager vortex clusters form in steep traps but are suppressed in harmonic traps.

Evaporative heating efficiency is unaffected by trap shape.

Vortex-antivortex annihilation requires at least three vortices.

Abstract

We study computationally dynamics of quantised vortices in two-dimensional superfluid Bose-Einstein condensates confined in highly oblate power-law traps. We have found that the formation of large scale Onsager vortex clusters prevalent in steep-walled traps is suppressed in condensates confined by harmonic potentials. However, the shape of the trapping potential does not appear to adversely affect the evaporative heating efficiency of the vortex gas. Instead, the suppression of Onsager vortex formation in harmonic traps can be understood in terms of the energy of the vortex configurations. Furthermore, we find that the vortex-antivortex pair annihilation that underpins the vortex evaporative heating mechanism requires the interaction of at least three vortices. We conclude that experimental observation of Onsager vortices should be the most apparent in flat or inverted-bottom traps.